Calculating pediatric doses. Often our medication inserts will have a pediatric
dose available to us for drugs that are commonly used in children. Now we can't
do research on children because that is unethical but this data comes from a historical review
of medications used and the outcomes ,and adverse events. But what do we do we
don't have any information on children dosing and I have a medication that's
being prescribed to a child? Well we're going to show you some formulas say that
you can use that take into consideration the patient's age, their weight, and body
surface area so you can make sure you're giving the right dose to your child - and
we're going to do all of that right after this. Welcome back my name is Tammy
and this is NurseMinder and on this channel we do everything nursing so if
you're new here consider subscribing below so that you get the next video
when it's released. So one of the reasons that we have to calculate a different
dose for children is because they work with medications differently.
Remember how pharmacokinetics - we talked about this in a previous video - how the
body absorbs medications, how it breaks it down metabolizes it, distributes it
and excretes it. Well the child's body is different. The
organs sometimes are a little bit less capable of functioning the way that
the adults does, so we need to create a dose that's safe for them but still gets
us the therapeutic outcomes we're looking for. We're going to start with
age first. It's probably the easiest calculation to do and we don't require
any tables or diagrams, so we're simply just gonna take the data we have to make
sure we have the right dose. We have Fried's Rule first and this is for
children less than one year. I should write that in here. Less than a year old.
So maybe you have a "fresh infant" to help remember that Freids rule applies to
months. So a child's dose is equal to the age in months, divide that by 150, and we
get this number because we assume that the adult dose is based on meet someone
who is 12 and a half years which is equal to a hundred and fifty months. So
that's an assumption we need to know off the top. So again for Frieds rule, less
than year, a child dose is age in months divided by 150 - that's our number
of months for a adult dose - and then we multiply that by the average adult dose.
So for example if I want to give Tylenol to my infant, they've got a fever, and
there's six months old, and I don't have any information on the package insert
I can do a quick calculation. Six months / 150 months
times by 650 milligrams. When I calculate this all out my months will cross off
I'm left with milligrams. It means I'm going to give 26 milligrams of Tylenol
to a six month old infant. If I'm working with somebody who is over that one year
mark, we are actually going to use their age in years. And this is where Young's rule comes in.
You can think of this as years, Young - youth 1 to 12. Frieds was for infants.
We're gonna use months there. So in Young's rule we're going to use their
age in years. We divide that by their current age plus 12 and then multiply
that by the average dose of that medication for an adult. So if I've got a
four year old and I still want to give Tylenol - there are four years old - I
divide that by four years plus 12, my years will cross out. So now I've got four
divided by 16 multiplied by 650 and it gives me one hundred and sixty two point
five milligrams. A really quick check to make sure that your medication that's
ordered is the safe dose for your child or infant. Now it's your turn. You've got
a three month old infant and the average adult dose of this medication is 400
milligrams what is your dose? Similarly, finish calculating out if you had an
eight-year-old child and the average dose was 400 for an adult, what would be
the dose you give that child? So go ahead and pause this video, complete your
calculations and then press play when you're ready. Alright so what I'm hoping
you've found out is eight milligrams would be your infant dose based on the age and
the average adult dose for this medication.
And if you were giving that same medication to a youth of eight years old,
that your dose would be a hundred and sixty milligrams.
Let's move on to weight. So we can also use the patient's weight to make sure we
have the correct dose for our patient. In Clark's rule we're making the assumption
that the average male adults is a hundred and fifty pounds and most
pharmacological studies were done on males, and so that's why we use the
average male weight. Okay so this is the same number that we use for children's
age we used two hundred and fifty months so this time we look at pounds though.
So we have the child dose is equal to the child's weight in pounds divided by
a hundred and fifty pounds times by your average adult dose. So go ahead and
figure out if you have a child that weighs 54 pounds and the average dose is
650 milligrams what will be your dose? Pause this video and return when you're
done. Okay so that should be relatively straightforward we have 54 pounds
divided by a hundred and fifty pounds times by the dose of 650 milligrams.
After my pounds cross off, I'm left with milligrams, and my dose is 234 milligrams
for my child that weighs 54 pounds of a medication whose regular adult dose is
650 milligrams. Next we're gonna look at body surface area. So using a nomogram,
we are going to be taking our patient's height in either centimeters or in inches and
we're going to be lining that up with their weight and either pounds or
kilograms. Let's just say I have a patient who is a hundred centimeters
tall and they weigh 50 pounds. I'm gonna take my ruler here and I'm going to line
up my 100 centimeter tall to my 50-pound patient. This now will then intersect
with my surface area and it's going to give me a value. And it looks like it's
0.82. So if I look at that line - I'm just gonna move my measurement away -there's
zero point eight and there's zero point nine which means each of the line is
worth a point zero two. So point eight, point eight two, point eight four, point
eight six, zero point eight eight, point nine.
And I was at that first line. So 0.82 meters squared. Okay so based on my
nomogram with someone who is 100 centimeters tall and is 50 pounds I came
up with a surface area of 0.82 meters squared. So the next thing is to plug
this into my formula . Te formula for body surface area calculations is very
similar to the formulas have been doing in the past. The difference is for taking
our service area, so zero point eight two divided by one point seven three and
then timesing that by the average adult dose. So with that, go ahead and
figure out what my what my dose will be based on my surface area. Awesome! So what
you should have is three hundred and eight milligrams. So I left this 308.09
in here because I want to talk about the rounding rules. When it
comes to decimals, the rounding rules say that if it is less than 0.5 we're going
to round down. If it's greater than or equal to 0.5 then we're going to round
up. So because I have 308.09 - that's less than 0.5, it will be
three hundred and eight. If it was 308.52,
we would go up to 309. So just to remember that the
rounding rules do come into play here when determining your calculation. So we
have covered four different ways to make sure that your child's dose is
calculated correctly. We've gone over Frieds Rule, remember those less than a
year are done in months; Young's rule one to 12 years; Clark's rule is weight based
and in the nomogram is body surface area. So we have a variety of tools we can use
to make sure our patients get safe care. You know our medication rights involve us
knowing, as nurses, that the right dose is being given. So always check your doses
for accuracy, and until next time, make it a great day!! :)